The absorption of copper and gold is higher in the case of green wavelengths (500 to 540 nm) than for the wavelength of common laser types (≥1064 nm). In the laser welding of copper using laser pulses having infrared (IR) wavelength (1064 nm), the power of the laser pulse typically has a trapezoidal time pulse curve having a linearly rising pulse flank for generating a melting temperature and subsequently a vaporization temperature in the workpiece, a level pulse plateau for melt bath generation having a vapor channel in the workpiece, and a linearly falling pulse flank for ending the welding procedure. However, the welded workpiece surface has molten material spatters. In laser welding using so-called hybrid lasers, welding is performed simultaneously using laser pulses having IR wavelength (1064 nm) and having green wavelength (532 nm), to thus improve the energy coupling into the copper material. For so-called micro-weld bonds of copper, laser pulses having green wavelength (500 to 540 nm) are used, wherein the welding penetration depths are at most approximately 0.2 mm.
Users sometimes have new (e.g., glossy) copper parts and sometimes have copper parts which are days or weeks old (e.g., oxidized). Therefore, the processing parameters have to be adapted to the age of the workpieces and/or to the surface composition in IR laser processing. In addition, the coupling of IR laser radiation varies so strongly within a newly ground surface of copper that spot weld differences occur.